On Wed, May 15, 2013 at 06:09:15AM +0200, Mike Galbraith wrote: > On Wed, 2013-05-15 at 02:26 +0200, Frederic Weisbecker wrote: > > On Tue, May 14, 2013 at 04:07:20PM +0200, Mike Galbraith wrote: > > > On Tue, 2013-05-14 at 02:57 +0200, Frederic Weisbecker wrote: > > > > On Sun, May 12, 2013 at 10:17:49AM +0200, Mike Galbraith wrote: > > > > > Greetings, > > > > > > > > > > Turning on new NO_HZ feature on my Q6600 box in master, I see that > > > > > tasks > > > > > accrue zero utime/stime. However, the same exact kernel on E5620 box > > > > > works fine, so it would appear there's a CPU dependency somewhere. > > > > > > > > Ah indeed, I just managed to reproduce the same issue. > > > > > > > > > > > > > > Is core2 expected to go dysfunctional with context tracking enabled? > > > > > CONFIG_VIRT_CPU_ACCOUNTING alone works fine in 3.9-stable, turn on > > > > > CONFIG_CONTEXT_TRACKING_FORCE, and CPU accounting stops working on > > > > > core2 > > > > > boxen only, same exact kernel continues to work just fine on E5620 > > > > > (Westmere) box. > > > > > > > > There was no known issue with core2. The box where I'm seeing the it > > > > is a Phenom quad core that had NR_CPUS=2. May be the issue is more > > > > likely to happen with this low number. I don't know. > > > > > > > > I'm investigating further. > > > > > > So with CONFIG_HAVE_UNSTABLE_SCHED_CLOCK, you can't mix sched_clock() > > > (pure tsc) with local_clock()/sched_clock_cpu(cpu). The former is > > > always quite a bit ahead of the later, so mixing clocks is a nogo on > > > crusty old (but beloved) core2 box. > > > > Right I have the same issue. So let's use local_clock() everywhere here, > > it takes care of unstable tsc. > > > > Does the following fix the issue for you? > > Yeah, both can use sched_clock_cpu() instead though.
Right, given that irqs are already disabled. I'm preparing the patch. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
